Matic electric inc



Aug. 2l, 1928.

J. wlcKs AUTOMATIC TELEPHONE SYSTEM Aug. 21, 1928.

:J. WICKS AUTOMATIC TELEPHONE SYSTEM Jahn .Hicks Aug. 2l, 1928.

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J. wlcKs AUTMAT I C TELEPHONE SYSTEM original Filed may 19, 1924 1Q Smets-sheet '7 @lum ,l La

BUS)l F/RST SELECTK KEPEATE To .smw ALARM,

J. WICKS AUTOMATIC TELEPHONE SYSTEM Original Filed May 19, 1924 V Q {fm} JMU?? l0 Sheets-Sheet 9 EP Conf/s cr:

Z. MHH-3!- J. WICKS AUTOMATIC TELEPHONE SYSTEM Aug. 21, 1928.

1o sheets-sheet 1o Original Filed May 19, 1924 Patented Aug. 21, 1928.

UNITED STATES PATENT OFFICE.

JOHN WICKS, OF OAK PARK, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO AUTO- MATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

AUTOMATIC TELEPHONE SYSTEM.

Application filed May 19, 1924, Serial No. 714,240. Renewed May 11, 1928.

The present invention relates to automatic telephone systems in general, but is concerned more particularly with automatic telephone systems in which talking battery b is supplied from a trunking switch (selector) rather than from a final switch (connector).

As to a number of its features. this case may be considered an improvement on my copending application, Serial No. 680,596, filed l December 14, 1923.

According to one feature ot this invention, the first selector repeater supplies battery during the impulsing period to the line relay of the switch to which it repeats impulses. so as to simplify the switch-over operation which takes place after the dialling is completed and before the conversation can start.

According to another feature ot the invention, arrangements have been made wherebyv a call originated in a so-called inverted oflice, i. e.. Yan office in which the first selector repeater feeds talking battery both ways. may be completed through a special incoming selector vrepeater to a called line terminating in an ordinary two-wire otiice in which the connector' switch feeds talking battery both ways.

According to another feature oit' the invention, novel circuit arrangements have been provided to enable a first selector repeater to switch straight through on certain calls like an ordinary two-wire selector, the repeating apparat-us being cut out of I he circuit. According to still another feature of the invention, special arrangements have been made whereby a system embodying the features of the present invention is made to cooperate with a director system of the gcneral type disclosed in the co-pending application ot Richardson et al., Serial No. 517,- S66, filed March 29. 1922, but more particularly of the type disclosed in the co-penduig application of Nelson, Serial No. 573,175, filed July 8, 1922A There are several other features and objects ot the invention which need not be dwelled upon here, as they can be best understood from a perusal of the detailed description which is to follow.

Reference may now be had to the accom- ]'ianying drawings comprising Figs. 1-11, inclusive, which show, by means ot the usual circuit diagrams, a suflicient amount ot apparatus .funployed in a multiiciiee melee phone system embodying the features of the invention to enable the invention to be understood and its utility appreciated.

As the invention is of such scope as to be applicable to a number of situations which may not be found in a single multioffice telephone exchange area, the disclosure in the drawings is not limited to any one multi-office system. Accordingly, Figs. 1-7, inclusive when taken together, illustrate a certain amount ot' apparatus in a Inulti-ofiice system composed of two or more so-called inverted77 oflices and one or more offices 0f the ordinary or non-inverted type; Fig. 8, taken in connection with Figs. 2 5, inclusive, discioses certain amount of equipment in a multi-ofiice system in which all otices are of the inverted type; and Figs. 9 and 10, when taken in connection with Figs. 2J?, inclusive, disclose a. certain amount of equipment in a mixed multi-office system in which directors are employed to register and retransmit the telephone numbers so as to direct the calls `according to the most economical trunking arrangements. Fig. 11 is a layout drawing which shows how Figs. 1J?, inclusive, should be placed together in order to be understood best.

Considering first Figs. 1-7, inclusive, Fig. 1 shows the party line` of substations A and A terminating at the exchange in the rotary line switch LS. The rotary line switch LS has access in common with other line switches in the same group to a number of lirst selector repeaters, of which only one is shown.

The first selector repeater of Fig. 1 may be used to establish a connection through the incoming selector repeater, F ig. 2, in an inverted oiiice, the intermediate selector, Fig. 3, and the connector, Fig. .4t to the line of substation B. This first selector repeater may be used also to extend the connection through the incoming'selector repeater of Fig. 6 in an office of the ordinary two-wire type, the two wire selector S, Fig. 7, and the connector C to the line of substation B and may also be used in connection with the intermediate selector of Fig. 5, which is denoted by a dotted rectangle, and the reverting call switch and the common reverting call ringing equipment when a connection is desired with another subscriber on the same line as the calling subscriber. It 'will also be understood. that the first selec lill tor repeater may be used to extend a connection to a subscriber in the local oliice through two intermediate selectors and a connector, in which case talking' battery is supplied to the calling line and called line both by the first selector repeater'.

The incoming selector repeater of Fig. 2 is reached over the two-way trunla'. line TL when the latter seized by a lirst selector repeater', such as the one shown in Fig. l. There a duplicate incoming selector repeuter on the left hand end ot the trunk line TL in the o'l'lice local to Fig. 1, which is used on calls coming back the other way when the trunk line TL .is seized by a Vtirst selector repeater local to the oliice in which the ini'romingselector repeater of Fig. 2 located.

ln order to enable the invention to be understmd best, a detailed description ot the operation of the apparatus shown will be given. First it will be assumed that the subscriber at substation A, Fig. 1, desiringJ to conversel with the subscriber at substation B, Fig. 4, removes his receiver.

lVhen the receiver is removed at substation A, line relay G energizes over conductors 2 and 8 and places ground on private normal conductor l at arn'iature 1l, thereby making the calling line busy to the connectors having access to it and closing a circuit through switching relay 5 and stepping mag net 7 in series. Line relay 6 also connects test wiper 14 to the junction ot switching relay 5 and stepping magnet 7 at armature 12. However, in case the trunk terminating in the bank contacts` upon which the wipers ol the line switch are standing is idle, this latter operation does'not have any particular utility and switching relay 5 energizes :immediately, seizing the trunk. On the other hand, if the said trunk is busy, switching relay 5 is short circuited by the ground potential encountered on the busy test contart by test wiper 1l and does not energize. ln this case, stepping magnet- 7, which interiulits its own circuit, is operated through test wiper lll and advances the wipers 18-15, inclusive, step by step in search et' an idlel trunk. lhen an idle trunk is reached, which trunk, it will be assumed, is the one coniprising conductors 17-19, inclusive, switching relay 5, being no longershort circuited, energizes in series with steppingmagnet 7. Stepping magnet 7 however, does not energize at this time, on account of the high resistance of switching relay 5. Upon energizing, switching relay 5 opens the' test circuit and prepares the holding circuit at armature 9 and at armatures 8 and 1.0 disconnects line conductors 2 and 3 from the winding of line relay 6 and ground, respectively, and extends them by Way of wipers 13 and 15, the bank contacts upon which they are standing, conductors 17 and 19, and the normally closed contacts controlled by armatures 54.-

and 57 to the upper and lower windings, respectively, of the double wound line relay ot the first selector repeater.

Line relay 82 now energizes over the calling line and closes its repeating contacts at armature 58 whereupon relays 39 and 40 energize in series over the following circuit: from ground by way oi? relay 8., resting contact and armature 57, normally closed contacts controlled by armature 79, armature 5e and its resting contact, working contact and armature 58, and relay to battery. Relays' 89 and LlOthereupon energize and the Ylatter opens a point in the circuit of relay 35 so as to prevent the latter l'rom operating upon the energization of switching relay lll, which to taire place subsequently. As a further result of the energization of line relay 82, it closes at armature 59 a circuit 'for release relay 83. telease relay 88 'hereupon energizes; opens a point in the circuit of release magnet l2 and prepares a circuit for vertical magnet 48 at armature 62; and at armature 61 places ground. upon release trunk conductor 18 through the normally closed contacts controlled by, armature (58, thereby establishing the usual holding circuit i'or switching relay 5 et the line switch LS beiore the slow acting line relay (i has had time to deenergize.

'in the first selector repeater, as a fur-i ther result o1 the energization of release relay 83, it places ground upon conductor 5l armature through the low resistance lower winding of the marginal relay 81, thereby closing a circuit through the normally closed contacts controlled by armature :tor the slow acting relajfY Relay 84 thereupon euel'gizes, but relay 8l does not energize on account of the relatively high resistance oi' relay 34. Upon energizing, rc-

lay Bel connect-s the upper talking condenser at armature 68 to the tone lead Z5 through the normally closed contacts controlled by the eleventh rotary step spring 47 and through oli' normal spring 4M and its resting contact. Accordingly, dial tone Yfrom the source Qlis transmitted back to the callingl subscriber to inform himv that he may new proceed to call the desired number.

vWhen the calling' subscriber i'nanipulates his calling device in accordance with the first digit in the desired number, the circuit of line relay 32 is opened' a corresponding number of times. Each time its circuit is opened, line relay 82 deenergizes momentarily and closesl at armature 59 a circuit through arn'lature G2 and its working contact and armature 8d and its restingcontact for vertical magnet 48. By the operation of vertical magnet 48, the wipers 86-88, inelusive, are raised step by step and come to rest opposite the desired level of bank contacts. llelay 87 is energized in multiple with vertical` magnet i8 through the resting lill) lll) ,throughout the vertical movement.

contact and armature 83 and, being slow acting, maintains its armature attracted Upon energizing', relay 37 closes at arn'iature 72 a circuit through armature 82 and its resting contact and off normal contacts tor stepping relay 38. Stepping relay 3S thereupon energizes and completes at armature 74 a locking circuit tor itseltthrough the interruptor contacts 50 and the off normal contacts 45 and at armature 75 prepares a circuit for rotary magnet 49. It will be noted that upon the operation of the olf normal springs, which. occurs at the first vertical step, spring 44 disconnects the upper talking condenser from ground through the dial tone conductor and connects it to the lower winding of the line relay. This bridges the upper talking condenser right across the line. This is done so as to permit the line relay 32 to respond more readily to the interruptions produced in its circuit.

At theend of the vertical movement, relay 37 deenergizes and completes the circuit of rotary magnet 49 at the normally closed. contact-s controlled by armature 72. Rotary magnet 49 thereupon energizes and advances the wipers Sti-S8, inclusive7 into engagement l with the first set of bank contacts in the selected level and, near the end et its stroke, opens the locking circuit ot stepping relay 3S at the interruptor contacts 50. Stepping relay 38 thereupon deenergizes and opens the circuit of rotary magnet 49 at armature 75, whereupon rotary magnet 49 deenergizes also and closes its interruptor contacts 50 again.

In case the trunk terminating in the first sot of bank contacts is idle, switching relay 41 now energizes and seizes the trunk. Assuming the trunk to be busy, however, switching relay 41 is short circuited by the ground potential encountered upon the busy test contact by test wiper 87 and does not energize. Stepping relay 38 energizes through test wiper 87 and closes 'he circuit of rotary magnet 49 again at armature 75, whereupon rotary magnet 49 energizes again and advances the wipers into engagement with the second set ot' bank contacts.

This alternate operation of stepping relay 38 and rotary magnet 49 continues as described until an idle trunk is reached, which trunk, it will be assumed, is the one comprising conductors 92494, inclusive. Then such idle trunk is reached, switching relay 41, being no longer short circuited, energizes in series With stepping relay 38 over the following circuit: from ground by way of the grounded conductor 51, relay 41, the eleventh rotary step contacts 46, interruptor contacts 50, ofi'l normal contacts 45 and stepping relay 38 to battery. Stepping relay 3S., however,r does not energize over this circuit on account of the high resistance of switching relay 41. U pon energizing, switching relay 41 opens the test circuit and places ground upon test wiper S7 at armature 30, thereby making the seized trunk busy iinniediately to the other switches having access to it; disconnects armature 72 oi relay 37 at arinature 82 so as to prevent a further operation of stepping relay 38; prepares a circuit ttor relaY at armature 81; disconnects the operating conductor from vertical magnet 48 at armature 84 and extends it to relay 34 at the saine time disconnecting the latter from the grounded conductor 51; and at 'armatures 79 and 85 connects up the wipers 86 and SS, at the saine time opening the initial circuit of relays 39 and 40 at the normally closed contacts controlled by armature 79. Relays 39 and 40, however, do not deenergize at this time, however, but are held up over the trunk line TL and through the two windings oi relay 107 oit the incoming selector repeater, 2, in series, relay 107 beiA g ln across unlline 'lli through armatures 121 and 122 otl the cutotl relay 101 and through the normally closed contacts controlled by armature 140 ol rel-.1 109 and the oft nornal contacts iv l energizes over the trunn line TL and in series with the relays 39 and and closes at armature 134 a circuit for the repeating relay 102 through the resistance 117. Relay 102 thereupon energizes and closes at armature a circuit for release relay 103 and closes at armature 123 a circuit through relay 109 as follows: from ground by way or the upper winding of relay 109, normally closed contacts controlled by armature 143, armature 123, upper winding of relay 105, and the upper winding of relay to battery. Relays 109, 105, and 10G energize over this circuit and relay 109 locks itselit' at ari'nature 139 to ground through armature 129 and its working contact of relay 105; shunts the upper talliing condenser across the tall-:ing circuit at armature 137 and consequently around the line relay 107 so as to improve the impulsing circuit; short circuits the resistaiice 117 at armature 133 so as to furnish more current to the repeating` relay 102; connects the upper winding o1' line relay 107 directly across the line at armature 140 at the saine time disconnecting the lower winding of the rclay; prepares a locking circuit itor stepping relay-108 at armature 141, thereby grounding 011e terminal ot the lower talking condenser; and at armature ,lisconnects the left hand terminal ot the now grounilid lower talking' condenser irom the lower talking conductor and connects it through the low resistance 119 to the repeating armature 134 of relay 107. This is'done so as to improve the response et the relay 102 to the interruptions in its circuit produced at armature 134.

106 are now maintained energized over conductors 161 and 163 of the intermediate selector, Fig. 3, line relay 201 being bridged across conductors 161 and 163 at the intermediate selector through the normally closed contacts controlled by arn'iatures 228 and 232 and conductor 163 being grounded in the incoming :felector repeater through Wiper 150 at armature 141 of relay 109.

1n the intermediate selector, Fig. 3, line relay 201 now cnergizes and closes a circuit from the grounded release trunk conductor 162 tor the combined release and change-over relay 203 atr armature 221 in series with the resistance 202. Relay 203 thereupon encrgizes; closes a locking circuit Vlor itself at armature 223, prepares a circuit lor stepping relay 204 at armature 224, at the same time opening a point in the circuit of rotary magnet 210; and at armature 225 prepares a circuit for vertical magnet 209 and opens a point in the circuit of release magnet 206.

Vhen the calling subscriber operates his calling device in accordance with the third digit in the desired number, the interruptions produced in the circuit of the line relay ot the rst selector repeater vare repeated to the incoming selector repeater and. are again repeated in the circuit of line relay 201 of the intermediate selector at armature 123 of relay 102 of the incoming selector repeater. Accordingly, line relay 201 dcenergizes momentarily for each interruption and closes at armature 223 a circuit through armature 225 and its working contact Yfor vertical magnet 209. By the operation ot' vertical magnet 209, the Wipers 233-235, inclusive, are raised step by step and come to rest opposite'the desired level oit bank contacts. Upon the closure of the oft normal contacts 205, a circuit is completed. tor stepping relay 204 which includes the Working contact and armature st aud contacts 207 of release magnet206. Relay 204, upon energizing, prepares a circuit lior rotary magnet 210 at armature 226 and at armature 227 closes a lockingcircuit l'or itscll from ground by way of the resting eentact and armature 231 and through the interruptor' contacts 211 of the rotary magnet 210 and ott normal contacts 212.

y As a further result of the operation of the oli normal springs upon the `first vertical ftep et the switch, the oil normal con` tacts 214 close and prepare a direct circuit tor the resistance 202. Accordingly, upon each subsequent energization of relay 201, relay 203 is .short circuited at armature 222. However, relay 203 will not deenergize immediately responsive to being short circuitcd. owing to the fact that a short circuitcd relai.'v slow acting. as is well known. .ilccordingly relay remains energized throughout the series of deenergizations of line relay 201. y

At the end ot the vertical movement, line relay 201 comes to rest in an energized condition and relay 203, being short circuited, deenergizes and completes the circuit of the rotary magnet 210. Rotary magnet 210 thereupon energizes and advances the Wipers 233-235, inclusive, into engagement with the first set of bank contacts, at the same time opening the circuit of stepping relay 204 at contacts 211. The remaining part of the trunk selecting operation is the same as has been described hereinbefore and the intermediate selector selects an idle trunk, which trunk, it will be assumed, is the one comprising conductors 236-238, inclusive. When this occurs, switching relay 205 energizes over the following circuit: from ground by way of the grounded release trunk conductor 162, switching relay 205, interrupter contacts 211, off normal contacts 212, and stepping relay 204 to battery. Upon energizing, switching relay 205 opens the test circuit and grounds test wiper 234 at armature 229; disconnects ground from armature 222 of line relay 201 at armature 231; at armature 230 disconnects the deenergized relay 203 from the release trunk conductor 162; and at armatures 228 and 232 connects up the line wipers 233 and 235, at the same time disconnecting line relay 201. In the connector, Fig. 4, responsive to ground being placed upon the release trunk conductor 237 by the intermediate selector, Fig. 3, a circuit is closed 'through olf normal contacts 310 for the lower windingof` the combined changeover and ring cut-0H relay 303. Relay 303 thereupon energizes and disconnects the operating conductor 315 from the rotary magnet 311 and connects it to vertical magnet 312 at armature 329 and atV armature 327 closes a point in the circuit of release relay 302. Also line relay 301, which is bridged across conductors 236 and 238 through the resting contact and armature 338 and off normal contacts 309 and the normally closed contacts controlled by armature 325, energizes over conductors 236 and 238 and in series with the upper windings of relays 105 and 106 of the incoming selector repeater, Fig. 2. Upon energizing, relay 301 completes a circuit at armature 321 from the grounded release trunk rconductor 237 through armature 327 and its Working contact for release relay 302. Release relay 302 thereupon energizes; connects the release trunk conductor 237 to the local holding conductor 316 at armature 323, at the same time removing ground locally from conductor 316; opens a point in the circuit of release n'iagnet 308V and locks itself to conductor 316 at armature 324 through the resting contact and armature 332 and the resting lou result of the energization of switching relay 306, it disconnects conductor 236 from line rela 301 and connects it instead to the small con enser 313 so as to permit a small amount` of the ringing current to pass back to inform the calling subscriber that the called subscribers bell is being rung. Switching relay 30G also opens the locking circuit ot release relay 302 and prepares a locking circuit for ring cut olii' relay 303 at armature 341. Release relay 302 now deenergizes and disconnects the lower terminal of line relay 301 from conductor 238, at the same time closing a point in the talking circuit. In

' the incoming selector repeater, as a result of the line relay 301 being disconnected, relays 105 and 106 deenergize. Relay 105, upon deenergizing, opens the locking circuit ot' the lower winding of the change-over relay 109 at armature 129, whereupon changeover relay 109 deenergizes and places the talking condensers in their proper position in the talking circuit at armatures 137 and 142; opens a further point in its own locking circuit and prepares a holding circuit for release relay 103 at arn'iature 139; removes the shunt from around resistance 117 at armature 138 so as to reduce battery consumption and so as to keep the low wound relay 102 from heating up, and at armature 140 disconnects the junction of the two windings of line relay 107 from the lower talking conductor, at the same time connecting the lower terminal ot' the lower winding' out relay 107 to4 the lower talking conductor through the high resistance 115. The two windings of relay 107 and resistance 115 in series are now bridged across the upper and lower talking conductors.

In the first selector repeater, Fig. 1, re lays 39 and 40 now fall back responsive to the inclusion of the high resistance 115, Fig. 2, in their circuit. Relay 40, upon deenergizing, closes at armature 78 a circuit for relay 35 as follows: from ground by way of armature 64 and its resting contact, ar1nature 78 and its resting'contact, armature 81 and its working contact, normally closed contacts controlled by armature 66, and relay 35 to battery. Relay 35 thereupon energizes; closes a. locking circuit for itself and opens its initial circuit at armature G6; prepares a circuitat a `mature 67 'tor relay 3G; and at armature (35 disconnects ground from armature 74 of relay 38 and shunts the lower winding of relay 31, The circuits remain .in this condition until the called subscriber responds.

When the subscriber at substation B res sponds to the ringing of his bell by removing his receiver, ring cut oit relay 303 of the connector energizes in the usual manner and closes a locking circuit for itself at armature 328, and at armatures 326 and 330 disconnects the line wipers from its own upper winding and ground and connects them to the talking conductors 236 and 238.

In the incoming selector repeater, Fig. 2. relays 105 and 10o now feed battery tothe called substation B and, consequently, relay 105 cnergizes over the called line., but relay 10G being differentially wound dees not energize at this time. Upon energizing relay 105 shunts high resistance 115 at arma ture 130 through armature 133 and its rest`v ing contact. f

In the first selector repeater, Fig. 1, relays 39 and 40 now energize responsive to the high resistance 115, Fig. 2, being short circu'ted, and relay 40, upon energizing closes at armature 78 a circuit through ai ure 07 and contact i'or the meter operating` relay 3G. Vteiay 30 thereupon energizes; opens the circuit of the slow acting relay 37 and closes a locking circuit for itsel'ii at armature 70; and at armature G8 applies booster battery to release trunk conductor 18 through the working contact and armature 71 and resistance 73, at the same time removing direct ground from release trunk conductor 18 at the normally closed contacts controlled by armature 68.

Responsive to the application ot' booster battery to release trunk conductor 18, which conductor is now connected to private normal conductor 4 ot' the calling line through test wiper 14 of the line switch LS and armature 9 and its working contact, the marginally adjusted meter 1G is operated to register the call.. This meter may be used, as shown, as a totalizer of outgoingcalls on a party line, or it may be used on au individual line as an indicator of the amount oiE charge to be assessed the subscriber on that line. In any event, the meter magnet 16 energizes and advances the associated number wheels in the usual manner to register the completed connection.

In the first selector repeater, the slow acting relay 37 deenergizes after an interval` responsive to its circuit being opened at armature of relay 36, and removes the booster battery from the release trunk conductor 18 at armature 71, at the same time reapplying direct groundto the said conductor 1S, The meter magnet 10 may be adjusted to maintain its `armature attracted after the booster battery is removed and until the calling line becomes idle, or if desired it may retract its armature when the booster battery is removed.

The calling and called subscribers may now converse witheach other as desired, and when they have iinished conversing they replace their respective rcceirers.

Assuming that the subscriber at substation B replaces his receiver tir-st, relay of the incoming selector repeater. Fig. 2. deenergizes when the called subscriber replaces his receiver and reinserts the high resistance ltlfi lle into the circuit, whereupon relays 39 and 40 or the lin-it selector repeater, l, re-

spond by retracting,n their armatures. The circuitsI remain in con ition until the (.:all'ng subi-ieriber replalifes his lili'hrn i3-e er at sul receiver .y b2 of the iirst sel circuit ot line suits to be :pointed out lereinaliier. i s a liurther rrr-:nit et the deem??l y.tum oit line relay et the lirst selefi, repeater, it opens the circuit oli the ciated release relay B3 at :armature 50, at the ame 'time incidentally aiiplyi ground to the oiwrating conduis-tor zlirrnigli armature 02 and its Werl-ring' contact. ythe slew acting nonv energizes through r. .mtnre Working Contact, but this. 'loes not have an f particular utility at thisl time.

After the interval itor Ywhich it is adjusted, the slew acti release relay 32% deenergiaes, removes ground from the .blesse trunk conductor 18 at arma 'e 0l. and also opens the lockingv circuits or relav lz'iaiid 30, permitting` these relays lo (lee-licencie. Responsive 'to `the removal et the freund potential Vfrom releazsie trunk conductor l0 the switching lrelay of the line switch ,liti deenergi'fzes. AS a further result ot the decnergisation ot release relay 33, it removes ground `from conductor :3l at armature 00, whereupon switching relay 4l deenergizces diffronnecting the wi rs tifo' and 88. As a 'further rrsnl oi' 'le decnerginaion or am, it opens the circuit ot the sion' acting relay 34 and the release mw t circuit at armature (i2. YRelease iet l2 non' ei Y through oil normal contacts -iif'l and restores the Wipers oiI the switch to their normal position in the usual manner. .l`hc circuit oit release magnet 42 is opened at ofil normal contac 4S when the switch Wipers reach their normal position. in the incem selector repeater., llig. 2, result of the above mentioned openingf ,i "he circuit et repeating' relay llli by line relay i0?. relay 102 (leen-ei "ses and opens the rirenit ol release relay i0l at armature i. .al"y. the slow acting relay 104 any par,-

this doeg nos have l, .rzi'i 1 t ai 1 f .n nanny .n uns time.

ic end. oiV 'the interval 'tor l the levi acting rele which it 1.0... .Y Jy?) ground from release trunk conductor 162 and opemne' the circuit ot switching relay lll). teni A re lill dcener; iecls the Wipers 148 and nation of a further result ot the def-energirelease relay 103, 1t opens the circuit ot relay 104 and closes the release magnet circuit at armature 127, whereupon release magnet lll energizes through ott normal contacts 112 and restores the switch to normal in the usual manner. i pensive to the removal of ground fron release trunk conductor 162 ot the intermediate sinector, 3, switching relay 205 ot the intermediate selector, relays 303 and G oi2 the connector and switching'relay 349 of the line switch LS deonergine. Responsive to the deencrgization of switching relay 205 ot the intermediate selector release magnet 200 energiaes through olf normal contacts 200, resting' contact and armature 225, resting contact and armature 222, and armature 231 and its rr n cont :iet and restores the Wipers oi the sivitcn to normal in the usual manner.

Release magnet 206 also opens the contacts during the .releasing operation due 234 rotating back over grounded o test Wiper et contact in the connector, Trig. 4, responsive to the l/znergization ot relay 300, release magnet 0.7 energines through oli normal contacts 00, resting contact and armature 324, restn contact and armature 332, resting Contact and armature 341, and the normally closed contacts controlled by armature 3 3 to battery and restores the switch to normal in the usual manner. The entire connection is nonv released.

it will nonT be assumed that the subscriber at substation A, Fig. l, desires to converse Withthe subscriber at substation A on the same line. ln order to do this it Will be necessary 'for the subscriber at substation A to call a special number Which Will result in a connection being extended to a so called reverting call switch and thence to a special ring-back set which. Will'ring the bells of the tivo subscribers alternately. Accordingly, the subscriber at substation A removes his receiver and it will be assumed that the line sivitch LS selects the iirst selector repeater shown in the drawing, and that when the sul criber manipulates his callingV device in accordance with the .first digit in the desired number the iirst selector regeater selects the trunk comprising conductors )9l, inclusive, extending to the intermediate selector, Fi 5. This intermediate selector is denoted by a dotted reci ngle, but may identical with the intermediate selector shown at Fig. 3.

YWhen the calling subscriber manipulates his calling` device in accordance with the second digit in the desired number, the intermediate selector raises its wipers 400403, inclusive, opposite the desired level of bank contacts and selects an idle trunk, which trnnlr it u'ill be assumed is the one comprising conductors 404406, inclusive. When Uli this occurs, line relay 412 of the reverting call sviteh energizes over conductors 404 and 406 and closes at armature 436 a circuit for release relay 415. Release relay 415 thereupon energizes and places ground on cogiductor 40T at arn'iature 403, and armature 442 opens a point in the circuit of release magnet 423 anc1 a clrcu stepping; magnet 424, switch for operation.

lflhen the calling subscriber manipulates his calling: device in accordance with the third and last digit in tl the circuit ot line relay 412 is op responding nuinher of tinies in he descrioed Manner at the .first seltor repeater. Each tune line relay 4 2 deenergi'zes responsive to one of these interruptions, it closes at armature a circuit through (firinatnre 442 and its Working' contact, nornially closed contacts controlled by armature 445, and series relay 417 for stepping` .magnet 424. By the operation of stepping magnet 424 Wipers 421 and 422 are advanced step by the herein step and come to rest on the harm coi `ets in which conductors 469 and 410 terin late.

Relay 41.7 is energized in series with stepping magnet and, heingj slow acting. maintains its armature attracted throughout the s; ping movement. Upon enerhi. ingr. relay .i l closes a locking circuit for itself at armature 447, and opens a point in the circuit ot relay 411 at armature 446. Upon the first step of the switch oil normal. contacts 405 closee whereupon relay 416 e-.iergizes and a circuit tor release magnet at armature 444, at the san e tii'ne preparing a circuit tor relay 411.

At the end of the stepping movement relay 417 deenern Zes and clos' a point in the circuit ot relfjw 411 .1e/46,

The callingf suhserioer, ha /ing dlalled the special number according to previous i stru e 1,021 line relay 38 deenergises and opens the o i going control circuit at armature 58 and the circuit oit ig'elcase relay at armature 59.

In the reverting call switch, F responsive to the opening.; of the outgioii 1.,@

i circuit hy the first selector repeatei line 412 deenergsii-tes and compl its Working contact, wor contact iature 445, resting@ con act and ai 4G armature 448 er1 and disconnects 40S rozn line relay by Way o1" relay 419 an rey armatures 1:11. also c mature 432 beteru and 452ky resa ectively. Relay 1ad time to latter has really contacts controlled. by relay 440 to tunl conductor 405. The

lov-fe r n.

on account of the current drawn by t lon' wound relay 414, l11 le'. 5; locks itto the grounded release trunl: condi ctor l 1 armature 551, at the lier so as to :torni a holding cirthrougrli the switch; discon- Yfrom armature 59 of line relay .connects the Wipers S6 1e mel: bridge relays 40 and instead to the incorn- 17 and 19, at the same said conductors from the The conhrot gli the ci without any talking eed bridges and a pelli is provi whereby the ringing current may be projected hack to the callizzf.; line from the rino; equipment.

ln the 'ng call switch, 5, remo 've to connected up to the reundueto. 40'* as herefnbelore leaf-1e t nnli u),

' the low Wound .relay 414 enerinal relay 31 l a id conne( inli con i rey es with the ina;

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relector repeater and connects conducto 495 to ground v 1:.; t1 lar effect at of the fact that ctor is, for the time selector ree connection. held ojound applied to f conductor 41' of the reverting tlrrouggh armature 441 and its 1e contact and lhJ upper Winding 01"' .ceruinglyg relay 413 cneigizes the switching; relays of 'the and oli the first selector rel'v'len this i up selely through tha.r

series with relay 414 nu l sw.. n. all ot which are to the rlease trnnl conductor of :ish/ed ci'inneetion. Upon energgr 413 locks itself to the grounded con actor N7 at armature 439; sepits arati' the tivo windings of line relay 412, and connects the upper Windingr` to battery and the lower winding to ground at armatures 43S and 437, respectivel g and at armature 440 placesl ground directly on release trunl: conductor 405 independent of its o'ivn upper winding, at 'the same time disconnecting` relay 414 which promptly deenergrizes anl clone-1 a circuit through the Working contact and armature 4I-i3 and the normally closed contacts controlled by armature lor the` wi per connecting relay 451. Relay 451 therciu'ion energizes and closes a local locliingf; circuit tor itseli2 at armature 452, at the :ame time opening its initial circuit. llela, 0 also connects up the line wipers and 421 at armatures 451 and 453, re- :aieclircly 'lhe wipers 421 and are non' cr ted to the common rinsino' leads 40!) ai 40, over which rii current is rejected alternately. lfh A, ng currentl ons bach over the established connection o the calling' line and operates the bells at mitin-'tations A and il alternately.

lWhen the subscriber at substation A. respends to the ringing or' his bell by rem-oving' his receiver, the ring cut oil' relay 419 inthe reverting,` call switch, Fig. 5, operates in the Vveli lrnoivn manner and closes ari'i'iature 450 a circuit :tor relay 41S which thereupon energizes and locks itsel't to ground through ott normal contacts 425 at armature 449 and opens the circuit ot relay 411 at armature 448. Relay 411 now deenergrizes and opens the circuit ot release relay 415 at armature 482 and shifts the conductors 404 and 406 back to the line relay again, thereby removing,` the ringing current from the calling,y line. Line relay 412, which is now supplied With battery and ground locally, now t'ceds talking battery to the calling,- line and accordingly, energized and closes a circuit tor release relay 415 at armature :30 heitere it has had time to deenergize.

illhen the subscriber at substation A notes that his bell no longer ringing he knows that the subscriber at substation A. has responded and he talles ott his receiver, Whereupon the conversation may proceed.

vlllhen the conversation is terminated the tivo subwiriliiers replae their receivers and when they have both done so the circuit oit line relay 412 oi the reverting call switch is opened. iiccordingrly, line relay 412 deenergizes and opens the circuit of release rela)v 415 at armature 436. Release relay 415, upon deenergizing. closes at armature 442 a. circuit through the Working; contact and armature 444 ot the oli normal relay 416 for release magnet 423. Release magnet 423 new energizes and restores the Wipers 421 and 422 to normal position in the usual manner. When the normal position is reached ott normal contacts 425 separate, de-

energizing,- relay 416 and opening the circuit of release magnet 423 at armature 444.

As a further result of the deenergization of relay 415, it removes ground from the local locking conductor 407v at armature 443, whereupon relays 413 and 420 deenergire. Relay 413, upon deenergizing, removes lfreund Afrom release trunk conductor 405 at armature 440, whereupon the intermediate selector is released in the hereinbefore described manner. As a further result of the reuioral of ground potential from the release trunk conductor, switch through relay 31 ot the first selector repeater deenergizes and closes the release magnet circuit at armature 56, whereupon the irst selector repeater is restored to normal in the hereinbetere described manner.

1t will be understood that in case the subscriber at substation A desires to call another subscriber in his local oifiee, he operates a lirst selector repeater to some level other than the three levels shovvn, Whereupon the first selector repeater seizes an intermediate selector, Whose position in the train that ot a thousands selector. This intermediate selector may be identical vwith the intermediate selector shown in Fig. 3, l when it is operated in accordance With the second digit in the desired number it seizes a. similar intermediate selector whose position in the switch train is that of a hundreds selector. Accordingly, when the third digit is dialled this latter intermediate selector' is operated to seize a connector, like the one shown in Fig. 4, which then responds to the last two digits to complete the connection to the desired line.

ln order to explain how a connection is completed between a so called inverted oiiice and an ordinary tivo-Wire otiice, it Will be assumed that the subscriber at substation A desires to converse with the subscriber at substation B, Fig. 7, Whose line terminates in a two-wire ottice of the ordinary type, that is, one in which the connector in use is arranged to feet battery both Ways. It will be umed iturther that when the subfzcriher at substation A removes his receiver the line switch LS selects the irst selector repeater shown in the drawings, and that when the first digit in the desired number isdiallcd the first selector repeater, after raising' its Wipers to the desired level, sclects the trunk line TL con'iprising conductors 05 and 00, which extends to the incomine; selector repeater, Fig'. 6, in the distant ottico. Accordingly, line relay 501, Fig. 6, which is br'. Ted across the conductors oi' the trunk line TL through off normal contacts 512 and the normally closed contacts controlled by armature 535, energizes over the trunk line and closes at armature 52 a circuit through the resistance 517 for the 

